1. Field of the Invention
The present invention relates to a thermal recording material, and more particularly, to a thermal recording material excelling in image storability.
2. Description of the Related Art
Thermal recording materials are utilized in various fields because in general, they are inexpensive and recording equipment therefor is compact and requires little to no maintenance. As competition in the thermal recording material market has recently intensified, there is a demand for more advanced functionality that differs from the functions of conventional thermal recording materials. In order to meet that demand, intense research is being conducted in areas such as color developing density, image storability, and head matching in order to improve thermal recording materials.
In conventional thermal recording materials, 2,2-bis(4-hydroxyphenyl)propane (so-called “bisphenol-A”) is widely employed as an electron accepting compound, which reacts with an electron donating colorless dye to induce a color development. However, none of the conventional thermal recording materials has ever succeeded in providing satisfying sensitivity, background fog, image storage property, chemical resistance and head matching (sticking), all at the same time.
Japanese Patent Application Bulletin (JP-B) No. 4-20792 discloses a recording material employing N-substituted sulfamoylphenol or N-substituted sulfamoylnaphthaol as the electron accepting compound and states that such a (pressure-sensitive or thermo-sensitive) recording material achieves improvements in image density, image stability and cost. Nonetheless, there is still room for much improvement in image storability.